Induction Coilgun Research Articles

A Comparative Study of the Launching Performance of the Sleeve and Solenoid Projectiles Using a Four-Stage Induction Coilgun

A Comparative Study of the Launching Performance of the Sleeve and Solenoid Projectiles Using a Four-Stage Induction Coilgun

Performance Analysis of a Multimission Missile Launcher With Varying Projectile Weight Based on Multistage Induction Coilgun

Performance Analysis of a Multimission Missile Launcher With Varying Projectile Weight Based on Multistage Induction Coilgun

Study on the Performance of the Sleeve Projectiles of Different Materials and Dimensions Launched Using a Four-Stage Induction Coilgun

Study on the Performance of the Sleeve Projectiles of Different Materials and Dimensions Launched Using a Four-Stage Induction Coilgun

Four Stage Induction Coilgun System Design and Analytical Calculation of Electromagnetic Expansion Force on the Stator Coil in the System

Four Stage Induction Coilgun System Design and Analytical Calculation of Electromagnetic Expansion Force on the Stator Coil in the System

Analysis of the Differences in the Optimum Triggering Positions and Projectile Velocities in Multistage Induction Coilguns for Different Arrangements of the Drive Coil Current Directions

Analysis of the Differences in the Optimum Triggering Positions and Projectile Velocities in Multistage Induction Coilguns for Different Arrangements of the Drive Coil Current Directions

Optimization of Multistage Coilgun Based on Neural Network and Intelligent Algorithm

The parameter optimization of a multistage synchronous induction coilgun (SICG) is a time-consuming task. Traditional machine learning methods can accelerate the process by building predictive models, but they require separate modeling for an SICG with different stages, which requires numerous datasets and is a cumbersome process. This paper proposes a method for building a predictive model for an SICG with different stages based on a recurrent neural network (RNN). In this method, the feed time of a 2- to 10-stage SICG is selected from the standard orthogonal design table as the training and test datasets, and the current filament method (CFM) is used to calculate the dataset label. The gate recurrent unit (GRU) neural network is used to study the training dataset, and the predictive model has good accuracy with respect to the test dataset, with an average error of 0.022. The predictive model and a particle swarm optimization (PSO) algorithm are applied to optimize the feed time of the SICG with different stages. The results show that the three-stage SICG can achieve a muzzle velocity of 50 m/s for a projectile, while the maximum muzzle velocity of the three-stage SICG in all datasets is 46.87 m/s.

Multi-parameters study on underwater coil launch

The projectile launched by electromagnetic weapon has strong kinetic energy. In order to study the laws and characteristics of electromagnetic induction coilgun launching underwater, a multi-stage coilgun model was established in this paper. Based on the control variates method, the effects of trigger position, coil turns, capacitance value and other parameters on the launching process were studied, then the effects of above factors on the launching efficiency and exit speed were analyzed. The results show that the optimal trigger position offsets to the direction of the breech with the increase of the projectile speed; the optimal coil turns for a certain projectile and launching occurs when the trigger position is determined; the increase of the capacitance value can increase the exit speed of projectile, and the capacitance value should be selected according to the efficiency-speed curve when the launch efficiency is considered; the seawater resistance has little influence on the acceleration of the projectile, and comparatively large influence when there is no driving force. The research results of this paper can provide theoretical support for the manufacture of underwater coilgun prototype.

A Novel Technique to Arrest the Armature Capture Effect in an Induction Coilgun

In an induction coilgun, the exit velocity of the projectile (or armature) differs from its theoretical maximum velocity that can be achieved. This difference significantly depends on the pulsed power source (PPS) parameters and the armature (sleeve or solenoid) structures. It has been reported that the “armature capture effect” phenomenon is the cause of this velocity reduction. The armature capture effect must be nullified to achieve the maximum possible exit velocity or to increase the efficiency of the induction coilgun to its maximum possible extent. However, not much attention has been given to this issue so far. This article shows through computer simulation that the reduction in the projectile velocity can be arrested successfully if the drive coil current is commutated at the right instant. An SCR-based switching circuit for the drive coil current has been implemented in the induction coilgun under development in the laboratory. This article describes the SCR commutation circuit topology to commutate the drive coil current for an induction coilgun operating at high voltage and high current and compares the simulation results obtained with and without the current commutation for four different sleeve armatures of varying lengths but of fixed mass.

Developmental Studies on a Two-Stage Coilgun

This article presents the design, development, and operation of a two-stage induction coilgun developed at the Pulsed Power Laboratory of the Indian Institute of Science, Bengaluru, India. The first two stages of a four-stage induction coilgun have been fabricated and operated in synchronization successfully, launching a 37-g projectile to 28.9 m/s using for each stage a 252-J pulsed power source (PPS). This article shows the computational analysis and the experimental results obtained using the two-stage coilgun developed. The following parameters, viz., number of winding layers of the drive coil, number of winding turns per layer of the drive coil, and the projectile length are varied, keeping the PPS parameters as well as the projectile’s outer diameter and mass fixed. The simulation is carried out using a finite element method (FEM)-based software, Ansys Maxwell, and the results are then experimentally verified. Finally, an empirical relationship between the projectile velocity and the charging voltage of the capacitor bank is presented in this article.

Design and Simulation Results of a Multistage Induction Coilgun Using the Taguchi Method for Launching a 1000-Kg Projectile

Our previous design procedure for a multistage induction coilgun using the Taguchi method, which determined the turns and the layers of coil, was established and applied to a four-stage induction coilgun capable of launching a 100-kg projectile to a maximum velocity of 27.4 m/s. However, the ignition position, where the pulsed power is applied, is still not optimized yet even though the system purpose was accomplished. In this article, we suggest new design procedure and the control system for a multistage induction coilgun using the Taguchi method, which is capable to determine the ignition position concurrently with the turns and the layers, and the calibrated design was added to overcome the limitation of the Taguchi method. This new procedure is applied to design a four-stage induction coilgun for launching a 1000-kg projectile to a velocity above 20 m/s. The simulation results show that the design model was capable of launching a 1000-kg projectile to a maximum velocity of 26.43 m/s with a 6-kV charging voltage.

Effect of Mutual Magnetic Flux Linkage Between Stages of an Induction Coilgun on Its Performance

In a multistage electromagnetic induction coilgun (EIC), the time-varying magnetic flux generated by the first stage (or coil) links with the coils in the subsequent stages and induces EMF across their terminals. The magnetic flux linkage and the induced EMFs depend on the distance between the stages (or coils). This induced EMF circulates a current through the coils in the subsequent stages, if allowed to flow by such means of the pulsed power source (PPS) connection with these coils, i.e., it depends on the winding direction (clockwise or anticlockwise) of the coils and the connection of the crowbar diode (CD) in the PPS circuit. If CD is connected in parallel to the capacitor bank, then the main series switch averts this induced current flow through the coil, but if CD is connected in parallel to the coil following its winding direction, then induced current flows through the coil. In this article, the effect of this induced current on the projectile motion inside a multistage EIC is analyzed using hollow projectiles of different lengths but of fixed mass and outer diameter. Computational analysis is performed using a finite element method (FEM)-based software, Ansoft Maxwell, with excitation given only to the first stage. The results are then experimentally validated with a two-stage EIC facility developed. Only two stages are considered since farther stages will have insignificant magnetic flux linkage with the first stage and the projectile. For each projectile, the distance between the two stages (or coils) is varied, starting from 2.8 to 14.8 cm with a linear step of 1 cm. The results indicate that the projectile motion is affected in a multistage system, depending on the distance between the stages and the projectile length. The analysis will be beneficial for maintaining a suitable distance between the stages in a multistage type of EIC.

Multiphysics Simulation of Synchronous Induction Coilgun Based on Implicit Function and Level Set Method

The launch of synchronous induction coilgun (SICG) is always accompanied by strong thermal and structural effects, which will cause serious damage to the structure of the armature, and multiphysics computation is an effective means to avoid this problem. Compared with the conventional circuit-based model, the finite-element analysis (FEA) is more suitable for the multiphysics computation of SICG, but it is also more time-consuming. In this article, the implicit function and level set (IFLS) method is introduced to rapidly simulate the multiphysics problem of SIGC based on FEA. The armature is modeled implicitly in the material domain and the position of it is updated through the implicit function, avoiding the moving mesh and remesh problems in the arbitrary Lagrangian–Eulerian (ALE) method, which is generally used to dealing with the dynamic mesh problem. Besides, the volume loss density and the Lorentz force per unit in the moving band are transformed back to the initial position to complete the coupling of the thermal and structural field and maintain the accuracy and continuousness of the simulation. A single-stage SICG model is established with the ALE and IFLS methods, and the results show that the computation time of the IFLS method is nearly halved. Finally, the IFLS method is applied to the simulation of multistage SICG, and the computational efficiency is greatly improved.

Research on the Temperature Field Distribution Characteristics for Thermal Management of Coilgun

Ohmic heating has become one of the main factors restricting their efficiency and longevity of the synchronous induction coilgun (SICG) operating in a complex electromagnetic environment. Therefore, further exploration on the temperature spatial–temporal distribution characteristics of the SICG is of great practical significance to ensure its reliable and efficient operation. The single-stage SICG is taken as the research object to simplify the solving process. First, the effectiveness and accuracy of the numerical simulation models in terms of kinetic and thermodynamic properties are compared and verified. Then, the influence of different structural parameters on temperature rise and acceleration is investigated in detail. The conclusions can not only provide theoretical reference for the long-term service of the SICG but also guide the related research of continuous emission.

Design, Fabrication, and Experimental Results of a Pulsed Power-Based Four-Stage Induction Coilgun for Launching a Heavy Projectile

Since 2016, Hanwha Defense Corporation has been working on applying electromagnetic launch technologies such as induction coilguns to cold-launch systems that can launch guided missiles. First, a design procedure of a multistage coilgun system based on the pulsed power driven by capacitor banks was developed using the Taguchi method, and a laboratory-scale three-stage coilgun capable of launching a 21.68-kg projectile at a maximum speed of 27.5 m/s was built and the results of the experiment were announced in 2018. In this article, we design, fabricate, and present the experimental results of a pulsed power-based four-stage induction coilgun using the proposed procedure to prove the validity of the electromagnetic launch technology for heavy missile launch. In this experiment, a 100-kg projectile was fired under 4-kV charging conditions, the maximum speed of the projectile was 25 m/s or more, and an efficiency of 15% was achieved without considering the mass of the armature. In this study, by accelerating a 100-kg projectile to 27 m/s, the feasibility of an electromagnetic launcher developed for heavy missile launch was verified.

Design, Simulation, and Parameter Optimization of a MultiStage Induction Coilgun System

This article proposes a method to design a three-stage induction coilgun system using the finite-element method (FEM). The system is designed to launch a 21.5 kg projectile. The method which is used to calculate the mutual inductance and the mutual inductance gradient between the two coils is expressed. Furthermore, the variation of mutual inductance and its gradient with respect to the distance between the two coils is indicated. The system parameters (i.e., coil currents, mutual inductance, mutual inductance gradient, force, velocity, and magnetic field distribution) are calculated and analyzed utilizing ANSYS Maxwell software. To verify the performance of the initial design, its analytical model is developed and validated in MATLAB software. The results of the analytical model are compared with the results obtained from the FEM method, and it is shown that they are well-matched in all waveforms. Besides, the efficiency of the system is improved through optimization by applying a genetic algorithm (GA). In this way, the efficiency of the system is enhanced from 29% to 36.6% and also the muzzle velocity is increased from 128 to 143 m/s. This method can be used to design a large-scale multistage induction coilgun (MSIC) for launching massive projectiles and reach high velocities.

Exploration on Matching Characteristics of Slip and Turns of Multistage Synchronous Induction Coilgun

Synchronous induction coilgun (SICG) has received tremendous attention in the military and civilian fields, which can be attributed to their inherent excellent noncontact linear propulsion characteristics. Theoretically, the ferromagnetic projectile can be launched at hyper-speed by multistage coil relay propulsion. However, the consensus of the SICG on low-speed and large-load propulsion has made its medium-high speed launch a controversial topic, hampered in part by lack of in-depth exploration of simulation model. Based on the previous work, this article focuses on the matching characteristics of slip and turns in order to obtain more reasonable parameter design strategy for the high-speed SICG. First, the numerical simulation model of multistage SICG is constructed on the premise of idealized assumptions to describe the energy conversion process. Then, the concept of slip is explained and the calculation formulas of slip and turns are derived, respectively. Finally, the operating characteristics of the two matching strategies of slip and turns are analyzed. The conclusions obtained by theoretical derivation and simulation comparison can provide reference for the design of medium-high speed SICG.

Coilgun design and evaluation without capacitor

Capacitors with high voltage and capacity values are used in most induction coilguns that are designed and constructed. The fact that capacitors are quite bulky and slow in energy transfer and how a coilgun can be made without using capacitors is the study subject of this article. Two and four coil gun samples were made to find the essential components of an electric gun, and the results are reported in this article. The accuracy of the results is also confirmed by FEMM analysis for these models. The harmony of experimental and theoretical results shows that smaller and low cost portable electrical weapons can be a powerful alternative to firearms in the future.

Design of a Pulsed Alternator to Drive a Single-Stage Induction Coilgun

Pulsed alternators (PAs) are ac generators which are specifically designed to generate pulsed currents of very high magnitudes for a given duration. An induction coilgun is being designed and developed in the author's laboratory to propel projectiles of different sizes. The scope of this work is to design and develop a PA for the same. A single-phase, iron core, slotted stator, cylindrical rotor, and no-compensation topology of the PA has been selected for this application. For the parametric analysis, a coupled circuit model of the PA has been used by considering the correction factors which include the skin effect and the magnetic saturation of the iron parts of the alternator. Eddy currents induced in the rotor core have been modeled as one circuit on each axis. A number of designs have been modeled and simulated and their performances have been analyzed for different design variables of the PA. Peak current, projectile velocity, and the temperature rise of the coil per current pulse are the output parameters which have been analyzed for every design. From the parametric analysis, PA with a particular configuration has been selected which results in the desirable performance of the PA-coilgun system. The design has been validated by modeling the same in finite element method (FEM)-based software. The performance of the PA driving the coilgun has been compared with that driven by the capacitor bank, and the feasibility of the multistage operation using the PA has been studied.

Experimental and Computational Studies on the Efficiency of an Induction Coilgun

Armature design plays a significant role in determining the performance of an induction coilgun. In this article, aluminum projectiles of 10.5-mm length and 21.7-mm outer diameter but of different shapes and thicknesses are fired from different initial positions inside the barrel having an outer diameter of 25 mm and a thickness of 1.5 mm with the coil wound over it. The coilgun is powered by charging a 504-μF capacitor bank up to 800 V and discharging it through the coils of a three-stage induction coilgun. Experiments are also performed at different initial charging voltages of the capacitor bank. For each firing, muzzle velocity of the projectile and efficiency of the induction coilgun are studied. Positions and muzzle velocities of the projectiles are measured using infrared sensors. A maximum muzzle velocity of 23.86 m/s with a projectile of mass 2.8 g and a maximum efficiency of 0.76% with a projectile of mass 8.5 g have been achieved with the present hardware setup in the laboratory. Experimental results are analyzed using the transient solver of the commercial software, ANSOFT Maxwell. From the analyses presented in this article it is found that the projectile having the highest muzzle velocity has a thickness equal to the skin depth and has a uniform current density distribution along its thickness as well. This article concludes that projectile thickness being equal to the skin depth of the projectile results in significant increase in its muzzle velocity and reduction in its mass which is an important design consideration of the induction coilgun. Secondly, each projectile has an initial firing position which is the best to achieve the highest muzzle velocity i.e., the highest efficiency of the induction coilgun and this position depends on the dimension and shape of the projectile.

Study on the Characteristics of Magnetic-Field Arrangement of Synchronous Induction Coilgun

Energy-conversion efficiency directly determines the scale of the synchronous induction coilgun, which is an important index to evaluate the launch system. Therefore, the method of improving the energy-conversion efficiency is one of the hot spots in the electromagnetic launch research. By changing the direction of the magnetic field, the acceleration mechanism of the armature has changed. This article focuses on the characteristics of the magnetic field arrangement of the multistage synchronous induction coilgun in order to obtain the design method of the magnetic field. First, the acceleration mechanism of the armature is analyzed for the consistent and inconsistent directions of the magnetic field. The feasibility of changing the magnetic field direction to improve the energy-conversion efficiency and the correctness of the simulation model is verified by the experimental results. The variation in the armature velocity and the single-coil efficiency is investigated when the direction of the magnetic field changes once, twice, and thrice. The prediction model of the magnetic field arrangement is established. Based on this model, the magnetic field arrangement of the coils is predicted when the direction of the magnetic field changes twice or thrice and the parameters of the pulsed-power supply are changed. The predicted results are in good agreement with the simulation results. The influence of the caliber on the prediction result is analyzed. Finally, the prediction model of the magnetic field arrangement based on the armature velocity and the discharge-loop parameters under the efficiency threshold related to the launcher caliber is established. The prediction model proposed in this article can effectively improve the energy-conversion efficiency and provide a valuable reference for the design of the magnetic field of the multistage synchronous induction coilgun.